Environmental Engineering Department at the College of Engineering, University of Baghdad, held PhD dissertation examination titled:
“Novel synthesis and characterization of flash graphene from agricultural waste for combined adsorption\ Moving Bed Biofilm Reactor (MBBR) system for treating medical center wastewater”
By the student Enas Samir Abdulmajeed and supervised Assistant Prof. Dr. Hayder Hamid Abdulmajeed on Tuesday 2/9/2025, in the Environmental Engineering discussion hall. The examination committee consisted of Prof. Dr. Abeer Ibraheem Musa as Chairman, and the membership of Prof. Dr. Zyad Tariq Abd Ali, Prof. Dr. Nagham Kareem Obaid, Assist. Prof. Dr. Hussein Gabbar Kadhim and Assist. Prof. Dr. Mohammed Bahjat Abdul-Kareem. After conducting the public discussion and listening to the student’s defense, the dissertation was accepted. It was summarized as follows:
This study presents an integrated and sustainable approach for hospital wastewater treatment through the development of an innovative adsorptive material, Flash Graphene (FG), synthesized from orange peel (OP) biomass using the Flash Joule Heating (FJH) technique. The preparation process involved converting orange peels into activated carbon (OPAC) via physical activation, followed by rapid exposure to high-voltage electrical discharge within milliseconds to produce few-layer turbostratic graphene with distinctive physicochemical properties. The prepared materials were comprehensively characterized using advanced techniques. XRD analysis revealed a characteristic peak at ~26.1°–26.6°, confirming the turbostratic graphene structure. SEM and TEM imaging demonstrated the transformation from dense peel structures into a honeycomb-like porous network with an average particle size of ~40.5 nm. BET analysis indicated a remarkable increase in surface area 11.17 m²/g, while FTIR and Raman confirmed the presence of active functional groups (–OH, –COOH), enhancing adsorption and electrochemical interactions.Batch adsorption experiments were performed using real hospital wastewater collected from Al-Saddr Medical City (Najaf, Iraq) to evaluate removal of organic pollutants (BOD, COD, TOC, Cu²⁺), inorganic contaminants (PO₄³⁻, NO₃⁻, Cl⁻, , TDS, TSS), microbial indicators (E. coli, Salmonella, Shigella), and physicochemical parameters (DO, pH). Tests under varying conditions (contact time: 15–120 min, adsorbent dose: 0.5–2 g, pH: 5–8.5, agitation speed: 100–250 rpm) showed that FG outperformed OPAC in all pollutants, particularly at lower doses and shorter contact times, confirming its high adsorption efficiency and rapid response.
Equilibrium data fitted best with the Sips isotherm model (R² > 0.99), suggesting mixed adsorption on homogeneous and heterogeneous surfaces. Kinetic studies followed the Pseudo-Second-Order model (R² > 0.99), confirming chemisorption dominance, while the intraparticle diffusion model revealed multi-stage mechanisms involving boundary layer and internal diffusion effects .To translate laboratory findings into practical application, a hybrid fluidized column system integrating FG with a Moving Bed Biofilm Reactor (MBBR) was designed and tested under various conditions (bed height: 1–3 cm, flow rate: 0.2–0.6 L/min, influent concentration: (25–100)%, aeration rate: 0.5–1.5 L/min). The hybrid OPFG–MBBR system efficiently removed complex pollutants, including microbial contaminants. The Bohart well described breakthrough curves–Adams and Thomas–BDST models (R² ≥ 0.98), with removal efficiencies exceeding 90% for BOD, COD, and microbial loads under optimal conditions. Dissolved oxygen increased from 0.3 to 3.1 mg/L, while chloride concentration decreased by 83.5%. Comprehensive physicochemical analysis demonstrated sharp reductions in chloride (775 → 110 mg/L) and TSS (54 → 4 mg/L), alongside increased DO due to enhanced microbial activity. Although a slight increase in TDS was observed from microbial byproducts and carbon dissolution, pH remained stable within the neutral range (7.3–8.4), ensuring favorable biological activity. Furthermore, increasing MBBR carrier quantity promoted biofilm growth, though excessive carrier loading reduced effective bacterial removal due to lower contact efficiency. In conclusion, FG synthesized from agricultural waste (orange peel) via FJH represents an innovative, cost-effective, and performance adsorbent for hospital wastewater treatment when combined with biological MBBR systems.
The Recommendations of this dissertation.
In light of the findings and limitations of the current study, the following recommendations are proposed to guide future researchers aiming to build upon and further develop this work:
- Exploration of Alternative Agricultural Wastes
Investigate other low-cost agricultural wastes (e.g., pomegranate peels, date seeds, banana peels) as carbon precursors. - Extension to a Wider Range of Contaminants: To evaluate the system’s broader applicability, expand the analysis to include other contaminants, such as antibiotics, antibiotic-resistant bacteria, and microplastics.
- Long-Term Stability and Regeneration Studies: Perform comprehensive operational evaluations to determine the resilience of OPFG in continuous systems and explore regeneration methods to reinstate its adsorption capacity post-saturation.
- Development of Predictive Simulation Models: Develop computational models (e.g., CFD, COMSOL Multiphysics) to simulate fluid dynamics, mass transfer, and contaminant removal behavior within the hybrid column for process optimization.
- Improve the FJH device: Develop by changing number of capacitor, tube dimensions.
